
Preheat the oven to 350°F (175°C). Cut the parchment paper for the bottom of your two 9-inch cake pans and spray with gluten-free cooking spray. I like gluten-free coconut oil cooking spray.
In a large bowl cream together the softened butter and the granulated sugar together with a mixer until fluffy.
Add the pure vanilla extract, lemon extract, dried lemon peel, food coloring (optional), gluten-free flour, salt, and baking powder to the butter mixture and mix until combined.
Add the milk and mix until smooth.
Beat in the egg whites and mix on high for 2 minutes.
Pour half of the batter into the first 9-inch cake pan and then pour the rest of the batter into the second 9-inch cake pan.
Bake on the middle rack for 25-30 minutes, until a toothpick inserted in the center, comes out clean and the sides of the cake is pulling away from the side of the pan.
Cool the cakes in the pans for about 10-15 minutes. Allow the cakes to completely cool before frosting.
Frost the top of the first cake layer only before adding the second layer—this creates the creamy center filling.
In a large bowl beat the softened butter at medium speed, until smooth. Add the pyre vanilla and lemon extract and mix until fully combined. Add the powder sugar one cup at a time to the buttery spread mixture and mix until fully combined. Add gluten-free yellow food coloring for a brighter yellow frosting (optional).
You can add fresh berries, shredded coconut, or both to the top of the cake—or as a surprise filling between the layers.